Connect-Disconnect Apparatus for a Vehicle Drivetrain

ABSTRACT

A connect-disconnect assembly for a vehicle drivetrain configured to drive a vehicle with a surface engaging traction member. The connect-disconnect assembly includes a coupler located within a final drive element or gear of a final drive assembly wherein in a first position the coupler does not span a gap between the gear and a transmission drive element of a transmission. In a second position, the coupler does span the gap between the gear and the transmission drive element such that the gear and the transmission drive element are connected. The final drive assembly includes an access port to provide access to a user accessible drive actuator to move the coupler between the first and second positions.

FIELD OF THE DISCLOSURE

The present invention relates to a powertrain assembly for a motordriven vehicle and more particularly to a transmission and a final driveassembly of a drivetrain of the motor driven vehicle.

BACKGROUND

Vehicles can have a prime mover, such as an engine, for producing powerand a transmission assembly coupled to the prime mover to transmit thepower to a driveline or to a final drive assembly. The final driveassembly moves a sprocket or drive hub that drives the vehicle along asurface. Such vehicles, in different configurations, include one or moresurface engaging traction members such as wheels or tracks which aredriven by the final drive assembly. In many configurations, the outputof the transmission, typically a drive shaft, is connected to an inputof the final drive assembly.

At some point during vehicle operation it may be desirable or necessaryto maintain or service the transmission. To do so, the transmission canbe removed from the vehicle. In other situations, it may be necessary toremove the drive assembly from the vehicle. In still other situations,it may be necessary to tow the vehicle from one location to anotherlocation for repair or service. In each of these situations, the outputof the transmission is often disconnected from the drive assembly toperform the service. Alternatively, the final drive assembly can becompletely removed from the vehicle, but removal can be extremelycomplex and can be extremely time consuming.

In some tracked vehicles, such as military vehicles, an access opening,such as a hatch, can be provided for a technician to access the outputof the transmission so that the transmission output, wholly within theenclosed space, can be disconnected from the final drive assembly. Whileaccessibility to the access opening may not require any special tooling,the amount of available space to perform the disconnection andconnection of the transmission to the drive assembly is limited. Inother instances, the design of the final drive assembly and sprocket forthe track is such that there is either limited or no access through thefinal drive assembly by which to reach the transmission. A hatch may berequired on the interior of the vehicle for access. In other situations,the final drive assembly may need to be disconnected from the powertrain and removed from the vehicle before the transmission can beserviced. Service in these conditions can require a substantial amountof time and effort.

What is needed, therefore, is a means for connecting and/ordisconnecting a final drive assembly to or from a transmission outputwhich thereby reduces the amount of time and labor required duringmaintenance, repair, or towing of a vehicle. Moreover, it is furtherdesirable to provide a connect-disconnect mechanism that providesimproved access to powertrain components.

SUMMARY

In accordance with one embodiment of the present disclosure, there isprovided a means to either connect mechanical power transmitting shaftstogether or to disconnect the shafts, and thereby prevent the flow ofmechanical power from one element to another. The connect-disconnectfunctions are accomplished without removing the power transmittingelements (engine, transmission, final drive) from the vehicle, and suchfunctions can be quickly reversed and returned to a prior state. Thefeatures of a connect-disconnect apparatus provides axial motion ofcoupling components, and positively locates the coupling components ineither the connected or disconnected conditions.

In another embodiment, there is provided a connect-disconnect assemblyfor a powertrain of a vehicle, having an engine, a transmission, and afinal drive. In particular, the connect-disconnect assembly reduces theamount of time and effort to service or repair the powertrain. Inaddition, the amount of labor and time required to complete upgrades ormodifications to the powertrain is also reduced.

In still another embodiment, there is provided a vehicle drivetrainconfigured to drive a vehicle with a surface engaging traction member.The drivetrain includes a transmission including a transmission couplerand a final drive assembly configured to drive the surface engagingtraction member. The final drive assembly includes a drive elementspaced from the transmission coupler to define a gap between the driveelement and the transmission coupler. A coupling device is located atleast partly within the drive element and coupled thereto. The couplingdevice, in a first position, does not span the gap such that the driveelement and the transmission coupler are not connected by the couplingdevice. In a second position the coupling device extends from the driveelement to the transmission coupler a distance sufficient to span thegap to thereby operatively connect the drive element to the transmissioncoupler.

In an additional embodiment, there is provided a connect-disconnectassembly for a vehicle drivetrain including a transmission having adrive element, and a final drive assembly configured to drive thevehicle with a surface engaging traction member and having a gear spacedfrom the drive element to define a gap. The assembly includes a couplerlocated at least partly within the gear and coupled thereto. The couplerin a first position does not span the gap such that the drive gear andthe drive element are not connected by the coupler. In a secondposition, the coupler extends from the gear to the drive element adistance sufficient to span the gap to operatively connect the gear tothe drive element. A drive actuator is operatively coupled to thecoupler, wherein movement of the drive actuator moves the coupler alonga longitudinal axis toward the drive element a distance sufficient tospan the gap and to engage the gear to the drive element.

In a further embodiment, there is provided a method for disconnectingand connecting a transmission having a transmission drive element from afinal drive assembly having a final drive element. The final driveelement is spaced a distance from the transmission drive element todefine a gap therebetween. The method includes disengaging a rotatabledrive actuator from a rotatably fixed position to a rotatable positionand rotating the rotatable drive actuator to move a coupler from a firstposition in which the coupler is disengaged from the transmission driveelement to a second position in which the coupler is engaged with thetransmission drive element.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present invention and the manner ofobtaining them will become more apparent and the invention itself willbe better understood by reference to the following description of theembodiments of the invention, taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a partial perspective view of a tracked vehicle including afinal drive supported by a body of the vehicle.

FIG. 2 is a schematic drawing of a front portion of a tracked vehicleincluding a transmission, final drives, and vehicle tracks.

FIG. 3 is a schematic sectional view of a transmission drive element, afinal drive assembly drive gear and a coupling device illustrated infirst and second positions.

FIG. 4 is a schematic section view of a transmission drive element, afinal drive assembly drive gear and a coupling device illustrated infirst and second positions.

Corresponding reference numerals are used to indicate correspondingparts throughout the several views.

DETAILED DESCRIPTION

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art mayappreciate and understand the principles and practices of the presentinvention.

In a general sense, the present disclosure relates to the control oftorque transfer from one member to another. In one condition, a firstmember and a second member can be coupled or connected to one anothersuch that torque can be transferred therebetween, and in a secondcondition the first and second members can be decoupled or disconnectedfrom one another such that torque cannot be transferred therebetween.While this disclosure provides different examples of this control in avehicular application, the disclosure is not intended to be limited tothis application. One skilled in the art will appreciate varying aspectsof the present disclosure outside of the vehicular application providedherein.

FIG. 1 illustrates one embodiment of a front portion of a machine orvehicle 100. In the illustrated embodiment a front portion of a trackedvehicle is shown without the tracks. The vehicle 100 includes a body orhull 102 configured to support the various assemblies and components ofthe vehicle including a final drive assembly 104. The final driveassembly 104 is located in a cavity 106 provided in a side 108 of thebody 102. The final drive assembly 104 is held in the cavity 106 by aplurality of fasteners 110. The final drive assembly includes a drivehub 112 which is configured to support and to drive the track (notshown) of the vehicle 100. The drive assembly further includes a port114 defining an aperture through which a connect-disconnect mechanisminside the final drive assembly 104 is operated. A cap 116 is configuredto be inserted into the port 114 to cover the aperture and tosubstantially prevent the unwanted introduction of dirt or debris intothe final drive assembly. The illustrated final drive assembly 104 islocated on a right side of the vehicle. A second final drive assembly118 (not shown) is located on a left side of the vehicle.

FIG. 2 is a schematic drawing of a front portion 120 of the trackedvehicle 100 including a transmission 122. A transmission drive shaft(not shown) is operatively connected to the transmission 122 and to thefinal drive 104. The final drive assembly 104 is operatively connectedto a first track 130, or surface engaging traction member, through thedrive hub 112 of FIG. 1. The final drive assembly 118 is coupled toanother side of the transmission 122 which is operatively connected to asecond track 132. During operation of the vehicle 100, a prime mover134, operatively coupled to the transmission 122, drives the tracks 130and 132 by operation of the final drive assemblies 104 and 118, as wouldbe understood by one skilled in the art.

FIG. 3 illustrates a schematic sectional view of a portion of the finaldrive assembly 104 of FIG. 1 and of FIG. 2. While FIG. 3 illustrates thefinal drive assembly 104 illustrated on the right side of the vehicle100 of FIG. 1, the final drive assembly 118, located on the left side ofthe vehicle is substantially the same configuration. Consequently, thediscussion of final drive assembly 104 applies equally to the finaldrive assembly 118.

As seen in FIG. 3, the final drive assembly 104 is operatively connectedto the transmission 122 through a transmission drive element 140. Thetransmission drive element 140 acts as a transmission coupler 140, ortransmission output element, which couples the transmission output shaftto the final drive assembly 104. The transmission drive element 140 isoperatively connected to the transmission drive shaft. Rotation of thetransmission shaft, therefore, drives the transmission drive element 140for rotation about a longitudinal axis 146 of the transmission shaft.The transmission drive element 140 serves as the output of speed andtorque from the transmission and is preceded by elements of thetransmission 122 which alter the speed and torque delivered totransmission drive element 140.

During initial installation of the final drive 104 to the hull 102, thefinal drive 104 is located in the cavity 106 and fixed to the hull bythe connectors 110. The cavity 106 is located such that placement of thefinal drive 104 aligns a longitudinal axis 148 of a final drive element150 with the longitudinal axis 146. In one embodiment, the final driveelement is a gear. Once aligned, the final drive element 150 ispositioned to be operatively connected to the transmission drive element140 with a coupling device 152 which is located within a cavity 154defined by final drive element 150. The cavity 154 is generallycylindrical and is defined within the final drive gears by an interiorsurface including splines 156 and a smooth surface 158. In oneembodiment, the splined interior surface 156 extends along approximatelyone-half of the generally cylindrical cavity as illustrated. In otherembodiments, the splines extend more or less than one half the length ofthe interior cavity 154 along the longitudinal axis 148.

The coupling device 152 includes a generally cylindrical final driveinput shaft or coupling shaft 160 which is illustrated in a firstposition 162 and a second position 164. The coupling shaft 160 islocated in the first position 162, which is a retracted or disconnectedposition, to enable installation of the transmission 122 in the vehicle.While the coupling shaft 160 appears to include two pieces in FIG. 3,the illustrated embodiment includes a single piece or unitary couplingshaft, a portion of which is shown in the first position 162 and aportion of which is shown in the second position 164. An exteriorsurface 166 includes splines 168 which extend along the length of thecoupling shaft 160 and which engage the splines 156 of the final driveelement 150. Due to the cylindrical configuration of the coupling shaft160, the splines are arranged circumferentially about the exteriorsurface of the shaft 160. The connection of the transmission 122 toeither one of the final drives 104 or 118 is made by the coupling ofshaft 160 to transmission drive element 140 and thence to the finaldrive component 150.

The coupling shaft 160 is configured to move longitudinally along thelongitudinal axis 148 within the cavity 154 and longitudinally along theaxis 146 into a generally circular cavity 180 defined by thetransmission drive element 140. An interior surface of the transmissiondrive element 140 includes splines 204 which are configured to engagethe splines 168 of the coupling shaft 160. Once the splines 168 ofcoupling shaft 160 fully engage the splines 204, a connection betweenthe transmission shaft and the final drive element 150 is complete.

To fully engage the coupling shaft 160 to the transmission drive element140, the coupling shaft 160 is driven along the longitudinal axis 148 bya drive actuator 184. The drive actuator 184 is driven by a tool (notshown) which interfaces with a head 186 accessible through the port 114.Removal of the cap 116 from the port 114 reveals an aperture whichincludes a size sufficient to enable the tool to engage the head 186. Inone embodiment, the tool is a hex drive tool configured to engage a hexdrive head.

The head 186 is operatively coupled to an actuator 190 including splines192 configured to engage splines 194 of a driver 196, such as a drivescrew. The actuator 190 further includes external splines which engagecorresponding internal splines of a support structure 197 at aninterface 199. Actuator 190 and driver 196 are always engaged throughmating splines 192 and 194. Moving head/actuator 186/190 along axis 148between first position 201 and second position 203 causes actuatorspline 192 to slide longitudinally along mating driver spline 194 whichis axially-stationary. The drive actuator 184 is shown in a firstposition 201 (the topmost position as illustrated) and a second position203 (the bottommost position as illustrated). Engagement of the splinesat the interface 199 in the first position 201 prevents rotation of thehead 186. In this condition, the position of the actuator 190 is held bya resilient member 198, such as a spring, which directs the actuator 190toward the right as illustrated. To allow the actuator 190 to rotate thedriver 196, the tool which engages head 186 is moved longitudinally withpressure in the left direction as illustrated to compress the spring 198and to disengage the splines of the actuator 190 from the splines of thesupport structure 197. In this position, the actuator 190 (thebottommost position 203 as illustrated) is rotatable. Rotation of thetool when the spring 198 is compressed, therefore, is not limited androtates the actuator 190 and the driver 196 about the axis 148, whichmoves the coupling shaft 160 along the axis 148 for engagement with thetransmission drive element 140. More specifically, as illustrated inFIG. 3, rotation of driver 196 moves the coupler/nut 200, which movesthe coupling shaft 160, either through spring 206 if moving leftward toconnect, or through a stop 210 in the rightward disconnect direction. Inone embodiment, the spring is a cylindrical helical compression spring.

In the embodiment of FIG. 3, the driver 196 moves the coupling shaft 160by movement of a coupler 200, also identified as a nut 200. The coupler200 is disposed between the driver 196 and the coupling shaft 160. Thedriver 196 includes helical threads that engage helical threads of thecoupler 200 at an interface 205. The coupler 200 is also lockedcircumferentially to the coupling shaft 160 by means of spline interface202. The driver 196 is captured axially/longitudinally to restrict itstranslation to the left or right along axis 148. Since the coupler 200cannot rotate relative to shaft 160 and the driver 196 cannot translate,then rotation of the driver 196 moves the coupler 200 toward thetransmission drive element 140 such that engagement of the coupler withthe coupling shaft 160 moves the coupling shaft 160 toward thetransmission drive element 140 to engage the splines 168 with splines204 of the transmission drive element 140. Upon completion of theengagement of the splines 168 with the splines 204, the transmissiondrive shaft is coupled to the final drive element 150 to drive thetracks 130.

Rotation of head/actuator 186/190 induces rotation of threaded shaft(driver) 196 by means of the sliding, but always engaged splineconnection between mating splines 192 and 194. The driver 196 does nottranslate axially/longitudinally left or right as illustrated. The nut200 translates left or right along the axis 148 by means of threads ofthe nut 200 and the shaft 196 at an interface 205.

A resilient member or spring 206 is located between the coupling shaft160 and the driver 196. The spring 206 is compressed by the coupler 200between a first stop 208 and coupler/nut 200. To accommodate compressionof spring 206, the coupler can slide longitudinally along axis 148 atspline interface 202 without disengaging circumferentially from shaft160. The stop 210 is loaded directly by movement of the nut 200 duringdisconnect (disengagement) of splined shaft 160 from the internallysplined transmission output member 140. The spring 206 stores potentialenergy if coupling shaft 160 is not properly aligned with drive element140, the misalignment of which prevents sliding spline engagement ofsplines 168 and 204. Alignment of the splines 168 and 204 is induced viarelative rotation between the transmission drive element 140 and theshaft 160. Typically, slight circumferential rotation of drive element140 enables the spring 206 to release energy after which snap actionengagement occurs at the spline joint of drive element 140 and shaft160. The final drive element 150 and the transmission drive element 140move from a circumferentially misaligned position to an aligned positionto enable the coupling shaft 160 and the transmission drive element 140to fully engage.

While the spring 206 assists in aligning the coupling shaft 160 with thetransmission drive element 140, in another embodiment, as illustrated inFIG. 4, the drive actuator 184 does not include coupler 200, spring 206,first stop 208 and second stop 210. In this configuration, a driver 212,such as a drive screw, which is rotated by the head 186, includeshelical threads engaging helical threads of a coupling shaft 214 at aninterface 216. Rotation of the driver 212 therefore moves the couplingshaft 214 toward the transmission drive element 140. In this embodiment,an alignment assist mechanism is not included and consequently,connection and/or disconnection between the coupling shaft 214 and thedrive element 140 is made by rotation of the head 186 which moves thecoupling shaft 214 toward the drive element 140. Indexed alignment ofcoupling shaft 214 and drive element 140 is accomplished bycircumferential movement (rotation) of either drive element 140 or finaldrive gear 150. Relative circumferential motion of drive element 140 anddrive gear 150 can be made by starting the engine to provide motivepower to the transmission's steer system, and providing a slight steermotion at the output shaft 140.

The illustration of FIG. 4 shows the coupling shaft 214 in a disengagedposition 218 and a fully engaged position 220. As previously describedwith respect to FIG. 3, the coupling shaft is a generally cylindricalsingle piece or unitary coupling shaft. The coupling shaft 214 movesalong a longitudinal axis 222. The coupling shaft 214 is located in thefirst position 218, which is a fully retracted or disconnected position,to enable installation of the transmission 122 in the vehicle. Thecoupling shaft 214, in the second position 220, is fully engaged withthe transmission drive element. An exterior surface of the couplingshaft 214 includes splines 224 which extend along the length of thecoupling shaft 214 and which engage the splines 156 of the final drivegear 150 and splines 204 of the transmission drive element 140.

Under certain conditions in which the vehicle 100 no longer moves underits own power, such as resulting from engine or transmission failure,the final drive gear 150 is disconnected (if connected) fromtransmission drive element 140. To disconnect the final drive gear 150from the transmission drive element 140, the head 186 is rotated with atool in a direction opposite to the direction previously used to connectthe coupling shaft 160 or coupling shaft 214 to the transmission driveelement 140. Once disconnected, the vehicle 100 is towed to anotherlocation where repairs can be made. After repair, the coupling shaft 160or coupling shaft 214 is moved into engagement with the transmissiondrive element 140 to connect the final drive transmission drive gear 150to the coupling shaft 140.

Connection of an output of a transmission to a vehicle mounted finaldrive or gearbox is generally independent of the installation of thetransmission into the vehicle. Consequently, the present disclosureprovides a simple and straightforward connection of power transmittingelements without damage after installation of the transmission iscomplete. Likewise, disconnection of the drive elements from one anotherto allow removal of the transmission or to facilitate towing of adisabled vehicle without incurring damage to inoperative drive elementsis provided. In addition, the splined shaft 160 is positively locked ineither the “connect” position (complete engagement of the drive shaft160 with drive element 140) or the “disconnect position” (completedisengagement of the drive shaft 160 from the drive element 140). Thisdisclosure provides all of these functions and features in a compact,simple, and robust mechanism.

While exemplary embodiments incorporating the principles of the presentinvention have been disclosed hereinabove, the present invention is notlimited to the disclosed embodiments. Instead, this application isintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

What is claimed is:
 1. A vehicle drivetrain configured to drive avehicle with a surface engaging traction member, the drivetraincomprising: a transmission including a transmission coupler; a finaldrive assembly configured to drive the surface engaging traction member,the final drive assembly including a drive element spaced from thetransmission coupler to define a gap between the drive element and thetransmission coupler; and a coupling device located at least partlywithin the drive element and coupled thereto, wherein the couplingdevice in a first position does not span the gap such that the driveelement and the transmission coupler are not connected by the couplingdevice and in a second position extends from the drive element to thetransmission coupler a distance sufficient to span the gap to therebyoperatively connect the drive element to the transmission coupler. 2.The vehicle drivetrain of claim 1 wherein the coupling device includes acoupling shaft having a dimension sufficient to span the gap and a driveactuator operatively coupled to the coupling shaft, wherein the driveactuator is configured to move the coupling shaft along a longitudinalaxis of the coupling device a distance sufficient to span the gap and toengage the transmission coupler to the drive element.
 3. The vehicledrivetrain of claim 2 wherein the drive actuator includes a linearactuator member operatively coupled to the coupling shaft and to thedrive element, wherein the linear actuator member is configured to movethe coupling shaft along the longitudinal axis and remains at a fixedlocation along the longitudinal axis during movement of the linearactuator member.
 4. The vehicle drivetrain of claim 3 wherein the driveactuator includes a user accessible drive operatively connected to thelinear actuator member, the user accessible drive including a firstposition which prevents the gear drive from moving the coupling shaftalong the longitudinal axis and a second position which enables thelinear actuator member to move the coupling shaft along the longitudinalaxis.
 5. The vehicle drivetrain of claim 4 wherein the user accessibledrive includes a biasing member disposed between a portion of the useraccessible drive and the linear actuator member, wherein the biasingmember includes a first condition to bias the user accessible drive inthe first position and a second condition to bias the user accessibledrive in the second position.
 6. The vehicle drivetrain of claim 5wherein the coupling shaft includes threads configured to engage thelinear actuator member and the user accessible drive is configured torotate the linear actuator member to move the coupling shaft along thelongitudinal direction to connect and to disconnect the drive element toand from the transmission coupler.
 7. The vehicle drivetrain of claim 6wherein rotation of the user accessible drive in a first directionconnects the drive element to the transmission coupler.
 8. The vehicledrivetrain of claim 7 wherein rotation of the user accessible drive in asecond direction disconnects the drive element from the transmissioncoupler.
 9. The vehicle drivetrain of claim 8 wherein the useraccessible drive includes a user interface disposed at an externallyaccessible location on the vehicle, to provide direct access to the userinterface without disassembly of the powertrain of the vehicle.
 10. Thevehicle drivetrain of claim 9 wherein the linear actuator memberincludes a drive screw configured to engage threads of or a nutassociated with the coupling shaft.
 11. The vehicle drivetrain of claim10 wherein the drive actuator includes a shaft biasing member disposedbetween the drive screw and the coupling shaft, the shaft biasing memberconfigured to provide a biasing force to the coupling shaft along thelongitudinal direction, wherein movement of the drive screw toward thedrive element increases the biasing force in the event the couplingshaft and the drive element are circumferentially misaligned.
 12. Aconnect-disconnect assembly for a vehicle drivetrain including atransmission having a drive element, and a final drive assemblyconfigured to drive the vehicle with a surface engaging traction memberand having a gear spaced from the drive element to define a gaptherebetween, the assembly comprising: a coupler located at least partlywithin the gear and coupled thereto, wherein the coupler in a firstposition does not span the gap such that the drive gear and the driveelement are not connected by the coupler, and in a second positionextends from the gear to the drive element a distance sufficient to spanthe gap to operatively connect the gear to the drive element; and adrive actuator operatively coupled to the coupler, wherein movement ofthe drive actuator moves the coupler along a longitudinal axis towardthe drive element a distance sufficient to span the gap and to engagethe gear to the drive element.
 13. The assembly of claim 12 wherein thedrive actuator includes a drive screw configured to operatively engagethreads of the coupling shaft, wherein the drive screw is configured tomove the coupling shaft along the longitudinal axis and remains at afixed location along the longitudinal axis during movement of thecoupling shaft.
 14. The assembly of claim 13 wherein the drive actuatorincludes user accessible drive operatively connected to the drive screw,the accessible drive including a first position which prevents the drivescrew from moving the coupling shaft along the longitudinal axis and asecond position which enables the drive screw to move the coupling shaftalong the longitudinal axis.
 15. The assembly of claim 14 wherein thedrive actuator includes a shaft biasing member disposed between thedrive screw and the coupling shaft, the shaft biasing member configuredto provide a biasing force to the coupling shaft along the axialdirection, wherein movement of the drive screw toward the drive elementincreases the biasing force in the event the coupling shaft and thedrive element are circumferentially misaligned.
 16. The assembly ofclaim 15 wherein the user accessible drive includes a drive biasingmember disposed between a portion of the user accessible drive and thedrive screw, wherein the drive biasing member includes a first conditionto bias the user accessible drive in the first position and a secondcondition to bias the driver in the second position.
 17. A method fordisconnecting and connecting a transmission having a transmission driveelement from a final drive assembly having a final drive element spaceda distance from the transmission drive element to define a gaptherebetween, the method comprising: disengaging a rotatable driveactuator from a rotatably fixed position to a rotatable position; androtating the rotatable drive actuator to move a coupler from a firstposition in which the coupler is disengaged from the transmission driveelement to a second position in which the coupler is engaged with thetransmission drive element.
 18. The method of claim 17 wherein rotatingthe rotatable drive actuator includes rotating the drive actuator tomove the coupler along a path defined by a longitudinal axis of thetransmission drive element.
 19. The method of claim 18 furthercomprising engaging the rotatable drive actuator at the rotatably fixedposition after the coupler is disengaged from the transmission driveelement.
 20. The method of claim 19 wherein disengaging the rotatabledrive actuator includes moving the rotatable drive actuator along thepath defined by the longitudinal axis of the transmission drive element.